followup:
Since I was not able to backup the Handheld with the Desktop software, to make sure I have a backup of the 9700, I made an activation with another (empty) 9700, which worked fine.
Then I disabled the wireless backup, and activated the original BB, which also was ok. After this, I turned on wireless backup again.

The KB-article says, if you turn off and on the wireless backup, the entries in the sql database will be purged. However, If I look into the SQL table, they are still present. I am curious what happens in the next days.